Tube and air center heat exchangers, such as used in motor vehicle air conditioning system condensers, commonly have a plurality of parallel flat sided extruded tubes connected at opposite ends to a pair of headers. Air centers between the tubes facilitate efficient heat transfer to the surrounding area. The headers generally comprise a header plate with tube receiving apertures and a tank secured to the header plate to supply refrigerant and receive same from the tubes. The air centers are brazed to the sides of adjacent tubes and the tubes are brazed or otherwise bonded to the header plates along with the tanks to assure leak free joints.
To reinforce the assembly, it is known to provide internal brazed sections of the header to the tube plates, as disclosed in U.S. Pat. No. 4,971,145, issued Nov. 20, 1990 having common inventor and assignee. The patent discloses a heat exchanger header providing transverse projections in the tube header plate that are contacted at a point intermediate their length by corresponding projections formed in the tank header plate. Braze cladding alloy is provided on the plates for effecting brazing of the plates at their mating surfaces and the points of contact between the projections. This provides a rigid header construction consisting of only two plates with enhanced burst pressure strength that allows a reduction in plate thickness and/or increase in core depth as compared with prior designs. However, the dimple joint design has inherent stress risers therein.